


Saints Come Marching

by cthchewy



Series: Keyhole 'verse [4]
Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Alternate Universe - Modern Setting, F/M, Urban Fantasy, road trippin' with your dragon husbando
Language: English
Status: In-Progress
Published: 2020-06-14
Updated: 2021-01-29
Packaged: 2021-03-03 20:15:20
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 4,694
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24721423
Author URL: https://archiveofourown.org/users/cthchewy/pseuds/cthchewy
Summary: Byleth and Seteth trek through the wilds of Fodlan, going from legendary lakes to harsh deserts, and even into secret caves atop the highest snow-capped peaks.  They quest to find the ancient dragons of the world, for when the mighty beasts of legend awaken… they’ll be invited to the wedding.  It’s only polite to send invites to family, butsoinconvenient when they don’t leave forwarding addresses when they fly off for naps.
Relationships: My Unit | Byleth/Seteth
Series: Keyhole 'verse [4]
Series URL: https://archiveofourown.org/series/1645483
Comments: 33
Kudos: 63





	1. Indech

**Author's Note:**

> This is a continuation of the Byleth/Seteth engagement plot thread from “You’re the Key to My Cichol”, particularly chapters 2, 4, 10, 18, and 19. It’s maybe not necessary to read that, but might be better for context. Meeting Byleth’s side of the family (just Jeralt) happens in “Age is just a number...”

The windows are down. Wind blows through their hair as Byleth exits the Magdred Freeway onto the far less busy suburbs of Rowe County. They keep going north into the hills. The houses get larger and farther apart until there’s a long stretch of nothing.

And past that nothing, when her sputtering little sedan finally crests over that last hill, is Lake Teutates.

What they can see from above is pristine. A clear, calm blue, slight rippling on the water’s surface from the summer breeze. By the lake’s shores are a few grand estates and private yachts. Behind them, surrounding the water on all sides, is untouched forest. Behind that, towering mountains.

The peaks here don’t rival the mist-covered Oghma mountains where Garreg Mach is situated, but the Oghma mountains don’t surround a secret basin lake. Teutates glimmers like a jeweled eye, teeming with life. No wonder it’s been a place of worship since ancient times.

As they leisurely cruise down the path to the shore, Seteth looks out the window. His profile, when Byleth quickly glances at him, is as handsome as always. Sharp features, thin lips. His usually carefully arranged hair has been blown into disarray, just as hers has, leaving his pointed ears to poke out. He’s been growing more comfortable with them lately, and perhaps with a little more time, maybe in a year or so, he’ll finally feel safe enough to cut his hair above the ears. The usual severe set of his brows is relaxed, replaced by a hint of some soft sorrow from bygone days.

“We weren’t truly siblings,” Seteth says. “Perhaps cousins or some other more distant relations. Nabatea was considered a large settlement in those days. We were thousands strong, and while we were called Children of the Goddess, we weren’t _all_ personally born of Sothis.”

It’s a strange topic to break the silence with, but it’s all too rare for Seteth to speak freely of his past. Byleth will never be the one to stop him when he’s ready to share. She nods, easily accepting that he’s not a son of the supposed goddess who once walked this land. “Why not, though? Didn’t she have the power to do so?”

“Creation… seemed to take a lot out of her. Mind you, I was too young to have seen it myself, but I heard from other Nabateans that the birth of a true daughter involved copious amounts of bloodletting. The Goddess would bleed into the earth for a day and a night, and from the soil would spring an infant daughter, fully formed.”

“Sounds gross. Were they clones?”

“Er, possibly… They did all grow up to look almost exactly like her…”

“Huh. Like parthenogenesis.”

“I’m sorry, what?”

Byleth gestures as best she can with one hand still on the steering wheel. “There’s this type of lizard, all females. Reproduce by laying clone eggs… Ah. Dragons are lizards too.”

“I don’t think that has anything to do with it,” Seteth says. His tone could be taken as a reprimand, but he seems more amused than anything.

“True, regular lizards aren’t rumored to have extraterrestrial origins.”

“ _Excuse_ you, I believe the correct term is ‘heavenly’ or ‘celestial’.”

Byleth nods. “Right. Aliens. And the rest of you?”

Seteth breathes in deeply and opens his mouth to refute the ‘alien’ charge, but then he thinks better of it and just sighs. “Well, humans were around before Sothis arrived. She adopted human form to walk among them, and grew as close to some as if they were her children as well. They were given her blood whenever they grew weak or sick, and in time came to have a portion of her powers and gained some of her draconic traits. These people and their descendants made up the majority of the Nabateans.”

“So you _are_ human.”

He graces her with a soft smile. “Human enough. My ancestors were once fully human, at least until Sothis’ gifts altered their bloodlines. Unlike Sothis and her daughters, however, this _is_ my true form. I find the transformation into a sacred beast to be quite taxing and, to be honest, I wasn’t sure if I could even do it anymore.”

They park at the end of the dirt road, which winds only halfway across the lake. The civilized half, with its waterside mansions, is behind them. In front is the deep end, where the water is darker, cooler, and more foreboding. The grasses and reeds grow in wild snarls along the water’s edge. Currents push seaweed from other parts of the lake to pile up here, and there are areas where the lake appears almost swamp-like. It’s still beautiful in an untamed way; in a way that humbles you before the majesty of nature.

Atop the water there floats an ancient temple. They get out of the car and pull down the canoe strapped to the top of it. Saint Indech is probably sleeping in that temple, and he was Seteth’s best friend once upon a time, even if they weren’t actually brothers.

Indech is coming to the wedding, even if the worst scenario has come to pass and he’s gone feral and needs some sense smacked into him.

“You’ll do fine,” Byleth says. She thinks of the way Seteth in dragon form fought GMU’s Pond Monster. “When was the last time your not-siblings fought anything? You can take ‘em.”

“If it’s Indech? Definitely.”

They paddle to the entrance of the temple and call out, “Hello?” Their voices echo through the damp, moss-covered marble halls. No one answers.

The temple is nowhere near the size of the secret chambers under the university. It’s basically just one large, empty chamber. No one appears to be inside, and there doesn’t seem to be any secret entrances. They check the walls and the floor for hidden switches – nothing.

After an hour of this futile searching, they wander back out. Seteth’s brows are furrowed; he’s upset because he thought he knew Indech the best among the other saints, and he should have been slumbering in this temple that was erected in his name.

Byleth pokes his forehead wrinkles. “Maybe he’s gone out for a bit.”

“I doubt it. If he had awakened, he would have come to Garreg Mach.”

“Then we’ll keep looking,” she says.

It’s not a waste of a trip when Lake Teutates is so beautiful. There’s even a little rocky island a short distance away from the floating temple. It’s nearing evening, and not really worth heading back to town when they already have camping supplies prepared. They set up their tent on that little island, beneath the lone tree. Catch some fish and cook them over a simple fire.

And they fall asleep gazing at the stars, hands entwined.

In the morning they’re woken up by bird calls coming from the boughs of the tree. There’s a little nest there, and three babies stretching their necks way up high for mama bird to shove breakfast into.

The ground rumbles.

Bubbles form in the water surrounding the little island.

It rises! It breaches the surface!

“What dost thou seek, young mortals?” asks the turtle-like beast upon whose back they are sitting.

Seteth slaps the rock – the shell – beneath him in frustration. “Are you kidding me? Indech! Why aren’t you in the temple?!”

Saint Indech, in beast form, pauses the no doubt epic challenge he was about to propose. He instead says, “Oh, Cichol! Is that you? It’s been so long!”

“Yes, yes, it’s me. But _w_ _hat_ are you doing? And _w_ _hy_?”

The giant black beast looks as remorseful as a demi-god can. “The temple got stuffy after two centuries. I thought rising from the lake would be more _dramatic_. I’m just trying to help any young adventurers in need of a sacred weapon…”

“Take a look around you. This is not a world in which any young adventurers would need a bow to go to war.” Seteth gestures toward the sunnier side of the lake, where a couple of kids have come out from their vacation homes to frolic by the beach. Their ice creams have all dribbled down their hands as they stand still, gazing wide-eyed at the sudden appearance of “Teutie”, the legendary Lake Teutates cryptid.

“I suppose…” Indech sighs heavily. “I suppose I didn’t want to believe it, when I first saw the construction. I always regretted not finding a proper successor, and now it really is too late.”

Seteth drops down to his knees and wraps his arms around the base of the neck of his old friend. “Indech, you fool, don’t you know you have thousands of successors? Every student who walks through the halls of Garreg Mach can do so only because you instilled such a legacy of peace. And when they graduate, they bring your ideals out into the world. This world came about because of you, because you believed in the goodness of humanity.”

Indech’s neck curls around Seteth, and they hold their embrace for many long seconds. The enormous turtle-dragon-swamp-monster sniffles, and a single tear splashes down onto Seteth’s back, so large it’s like someone accidentally spilled a drink on him.

Finally, Indech uncurls, and he smiles a dragon-y smile. “I’m glad to see you’re doing well. And Cethleann, how is she? I don’t see her with you…” He swivels his head a bit to see the rest of his shell-island and spots Byleth. “Oh! And who might you be?”

“Byleth,” says Byleth. She raises her hand, realizes there’s nothing to shake, and drops it.

“My, ah, fiancee,” says Seteth.

Indech gasps. He whips his head back and forth and stands up, raising the island that is his shell. He shuffles round and round in joy while his passengers cling onto the tree for dear life. The birds in the tree screech in alarm. “Oh, how exciting!”

“Yes, we’ve come to invite you to--”

“You’ve come to invite me to the _wedding_?!” The sacred beast jiggles even more violently, his stomping causing waves to ripple out across the lake.

“Yes, if you could perhaps, ah, move to shore and resume your human form? We would love to show you how Garreg Mach has modernized.”

Indech does stomp and slosh his way to shore, and he crouches so that Byleth and Seteth can slide off his back. He doesn’t, however, transform back.

“Let’s go!” he says.

Seteth tries to reason with him once more. “Isn’t it uncomfortable, holding that form all the time? Look here, you’re so exhausted you couldn’t even keep the wings up!”

“Impossible! I’m the _Inexhaustible_!” he says. And then, when Seteth only keeps frowning at him, he takes the lead himself. “To Garreg Mach, eh? I know the way.”

Indech begins to amble out of the lake’s valley, taking the island with him. The tree on his back shakes with each step, and it’s perhaps through some miracle that the nest doesn’t fall. The birds in it continue to chirp in alarm as their home moves so strangely, but after a few more stomps they hunker down and let their landlord do his thing.

Byleth drives her shitty little sedan behind him all the way.


	2. Macuil

Out of all the Nabatean saints, it was Macuil who loved flying the most. Indech, though friendly, had a strong reclusive streak and often chose to hide in his shell underwater. Flying left him too exposed for comfort. Cethleann also preferred water even in sacred beast form. Back when she still transformed, she loved to flow along the coast and through the rivers of Fodlan, and sightings of her beautiful scales glinting under the sun were considered a good omen. Cichol did love to fly, but he didn’t like to transform. (Still doesn’t.) Wyverns are much more convenient.

And Seiros… Well, she had taken the deaths of their people the hardest, and didn’t seem to much like anything for a long time. She didn’t actively hate much, either, after that first wave of pure rage petered out. She was ambivalent. Numb, perhaps. In modern times they would probably call it clinically depressed.

Macuil, on the other hand, actively hated a lot of things. First and foremost, he hated people. He hated ‘the drivel these modern bards try to pass off as literature’, he hated ‘small children touching everything with their grubby, sticky hands’, he hated ‘today’s youth fornicating in public, have they no shame?’, and so on and so forth.

This last one Seteth learned from Byleth, as he was asleep when Macuil went on that particular rant. Apparently he came across some students – as they say in the common parlance these days – _doing it_ right outside the administration building one night, and discussing which teacher’s desk it would be most thrilling to defile too! He’d screeched – a very raptor-like call that various people later recalled hearing – and they fled while pulling their pants up. When the perpetrators of this most heinous indecency could not be later identified, Macuil had had enough. He tore out of his human skin, and the rest is history. (“He just started laying out his grievances, and at the end of it he said, ‘Filthy, disgusting animals, all of you! I’m taking a nap!’ and then yeeted himself out the window. I was only there to give him the math department’s nominees for the Dean’s List, but maintenance almost charged me for the window because other witnesses hadn’t come forth yet…”)

So yes, Macuil has many dislikes and very few likes. He likes flying. He likes magic. He likes Flayn and _tolerates_ the rest of their family. That is all.

In past eras it might not have been possible to quickly track down his location only knowing this much, but in the age of smartphones, anyone is capable of filming the dragon flying overhead. Byleth had merely checked the timestamps on social media posts featuring Macuil’s flight, and in less than a day had figured out he’d probably settled down somewhere in the desert in Sreng. Plenty of cryptid hunters had come to the same conclusion, but none could actually get close enough to speak with him once they went into the desert. Macuil called down magic sandstorms to blow them out if they invaded his personal space bubble, and that bubble could span up to a mile out if he was able to see them coming.

That’s one area in which the old ways are superior. These young cryptid hunters are nowhere near as competent as a battalion of holy knights would have been back in the day. And how do they suppose they’ll get near a “flying sandstorm monster” if they aren’t flying themselves? Do they really think they can chase down a Sacred Beast in a _dune buggy_? Honestly!

Seteth considers himself a sensible person. As such, he is riding a wyvern for this mission. Flayn is beside him on a pegasus she has named Sprinkles. Behind him, with her arms around his waist, is Byleth, who is also, uh, sleeping. Very deeply. Her face is smashed into his back and she’s drooling on him a bit…

…Or actually a lot. It feels gross, but he doesn’t have the heart to wake her.

Like this, they come up on Macuil from overhead, Flayn navigating toward the GPS point of the last Mysterious Sandstorm report. The sandy-colored, birdlike Sacred Beast is digging what looks to be a burrow. Seteth lets his brother sink his ass into the sand before signaling to Flayn that they’re about to descend.

The wyvern and pegasus have already fluttered down to Macuil’s eye level by the time he hears their wingbeats. The gigantic eye snaps open. The butt-wiggling stills. He’s trapped in the sand up to his forelimbs and can’t easily escape up or down.

“God _damnit_ ,” he growls. “What the hell do you _want?_ ”

“Hi, uncle!” Flayn waves cheerfully.

“Cethleann! How wonderful to see you. Have you come to chat?”

“Greetings, brother--”

“Oh, drop it. _You_ can say your piece and _leave_. I let you have your nap and you can damn well let me have mine!”

Seteth would be offended, but that’s just how Macuil is all the time. “Of course, of course. We’re planning something of a family reunion, you see, and it wouldn’t be complete without you. Indech is already waiting at Garreg Mach. The special occasion is actually because I’m getting--”

“No. I’ll not return to that detestable world.”

Seteth feels a tic forming by his left eye. He forges on ahead anyway. He has to be the bigger man. “Ahem. Because I’m getting married.”

The giant reptilian eye before him slowly blinks. Then, “No.”

“Come now, brother, don’t be unreasonable. When’s the next time we’ll all get to see each other again?”

“Oh, I don’t know, maybe some _other_ time, when it’s not you getting married! Again! You’ve only been awake for what, three, four years? How about instead of bothering me, you learn to keep it in your pants instead!”

“You _are_ coming back. You have to. It’s family obligation!”

“Over my dead body! I have absolutely no desire to see you tie yourself to some human hussy!”

All right, this level of rudeness is too much. Attacks against his own person are fine – that’s expected in sibling rivalries. But to besmirch Byleth’s good name? Unacceptable!

“What was that?! I’ll _drag_ you back by force if I have to!”

“Where’s your lance, Cichol? How will you bring me back ‘by force’ without your puny toothpick?”

“I donated it! And as for how you’ll get some sense beaten into you, I will _land_ this wyvern, and then I will transform and _snap your fragile little chicken neck in my jaws._ ”

“Pah! You, transform? Hahahaha! Thanks for the laugh, at least.”

A low growl rumbles out unbidden from Seteth’s throat. He can feel his fangs start to elongate, and he’s about to make good on his promise…

But then, Flayn brings her pegasus fluttering down in an arc, and then up until the top of her head nuzzles her uncle’s feathery chin.

“Will you come back for me, uncle? Pleeeease?”

Ah. This is exactly why they brought Flayn along.

Macuil pauses, shrinking in on himself a bit. “I-- I don’t know, Cethleann… Of course I’d love to spend more time with you, but you know I’m no good with crowds. Couldn’t we stay here instead?”

“But uncle, you haven’t been able to rest well at all these past few years! The humans keep disturbing you since they followed your flight here. We could help you find a better resting place after the wedding.”

Macuil looks about to protest, but he can’t resist his niece’s teary eyes and lip wobble. Flayn strikes the killing blow by patting the seat behind her. “You can ride with me.”

* * *

With a snort, Byleth wakes. “Hmmmnugh? Wha’happun?”

She looks around for a while, blinking against the harsh desert sun, and then her gaze settles on the sight of Dean Macuil in his human form, as tall and angry as ever. This time, however, he’s not thundering down the halls of the administration building.

…He’s comically hunched over, riding behind Flayn on Sprinkles the pegasus.

A look of recognition flashes across his face when he glances in her direction. “Oh, it’s you. Sitri’s kid. Should’ve recognized you by your scent. Your lineage has always reeked of Sothis. I guess I’m not surprised Cichol would be into that.”

“Sitri’s your mother? How did they know each other?” Seteth whispers back to her. He ignores how his brother basically called him a motherfucker.

Byleth shrugs. “She used to teach magical theory at GMU before she got married… And that’s also before magical theory classes got absorbed into the sciences, I guess. She was pretty old when she had me. It was a long time ago.”

Macuil harrumphs. “She had poor taste in men, and so do you.”

“Uh… Did I miss something?” What a strange thing for Macuil to say. She pokes Seteth, but he doesn’t respond.

“Uncle! I wanted to ask for your opinion on majors since I’m to start university soon!” Flayn’s interruption is very obvious, but also very welcome.

The brothers don’t speak to each other at all. It’s an awkward flight back.

(The event is even stranger for Byleth since it’s the first time in her life that she isn’t the source of the social dysfunction.)


	3. {Interlude: The New Pond Monster}

Miles and miles away, at Garreg Mach, Indech is humming cheerfully as he tours around the beloved campus that he hasn’t seen in, oh, a hundred and fifty years or so? Nearly two hundred now, it must be. He’d been in charge for twice that amount of time, and had seen many things gradually change during his tenure as Archbishop and then as the university’s first dean. What he sees now is very different though. To him it appears as a sudden departure from his last memories, and he keenly feels that there is a gap from then to now that he will never be able to experience. It was a hard choice to let go in the first place.

Most of the buildings look the same on the outside, but the libraries where legions of students once bent their heads to copy down notes are now filled with the hum of strange machinery, scribbles replaced with tapping and clicking, words magically appearing and disappearing on the light-slates before each young scholar. Macuil must have had a hand in this, he thinks. As the most magically skilled of the saints, the university must have flourished as a research institution under his care. It will be good to see him again, and perhaps to pick his brain about all these technological advances.

Even more amazing than that, Cichol, or Seteth as he’s calling himself now, had told Indech there would be more than _thrice_ the number of students on campus once the new school year began. It must be so lively! Even now during the optional summer term, in which many staff members have also returned home and courses are very limited compared to the usual, Garreg Mach appears to him as a bustling metropolis.

With hardly any effort, Seteth was able to round up enough student volunteers to clear out the debris on Indech’s back. They climbed up the tree on his back, safely removed the nest, dug up the tree, re-planted it in a little courtyard that also housed a statue of Indech himself (he blushes just thinking about it!), climbed back up to put the nest back in the tree, and then brought out these marvelous machines called “power-washers”.

A good time was had by all. Meaning, a water fight broke out. Indech of course joined in, soaking everyone with a few swipes of his tail.

But now he’s free to run about in human form once more. As much as he enjoys living under a lake, he must admit it’s difficult to maneuver in small spaces that way. And also, quadrupedal beasts can’t skip. At this thought, Indech skips a bit just because he can. It’s fine to be childish when no one’s around to see him.

One hummed song comes to an end as he reaches the greenhouse, but before he can begin another, he hears someone else humming nearby.

“Hmm-hm-hmm~ Eat up, cuties! You’ve gotta grow big and strong so I can move you to a better terrarium!” A young woman is tending to little tropical plants, and she sighs. “You’re so lucky… I wish I could hide in a terrarium all day and just wait for food to come to me… I’d want mine to be tinted glass though, as dark as possible. And bulletproof. Better yet, a turtle shell. If those can be bulletproof…”

Turtle shells _are_ pretty great, Indech thinks. He can relate to everything she’s saying. (He hasn’t tested the bulletproof part, but the thicker parts are definitely arrow-proof.) As a matter of fact, he likely had those exact same thoughts as a child, before mastering the sacred beast transformation. It was probably because he was such a wallflower in his youth that he ended up actually becoming a full blown turtle.

Indech steps closer, making sure to make just enough noise to be heard coming, but not enough to startle.

The shy girl senses him coming and immediately apologizes. “I-I’m sorry, am I in the way? I’ll be done soon!”

“Oh, no need. Take your time, dear.” He smiles at her, and it slowly grows wider as he comes to the realization that not only are they alike in temperament, but that she is also in a way a descendant of his. He can feel a fraction of his magic inside her.

Indech has never married or had biological children, but he had plenty of disciples back in the day. Like his siblings, he gave his blood to the ones he came to love most deeply and who proved they could keep a secret. He doesn’t know what happened to their families in all the generations since, but some of those lines must still be flourishing if the presence of this girl is any indication.

“What’s your name?” he asks. “I think there’s something special about you.”

She regards him warily. “Um, I’m Bernie. And I think there really isn’t.”

Indech scoots over just a little bit more, and flares his crest. Hers lights up in return.

“Aaaaah! What’s this? What’s happening? Why are we all glowy?! I swear I’m nothing special and I probably taste terrible, you don’t want to eat me!”

At the same time, he says, “Granddaughter! Do you want a magic bow? I _might_ be able to teach you how to grow a turtle shell too. Not too sure on that – none of my disciples have ever tried it – but even if it doesn’t work, we can share _my_ shell!”

* * *

Macuil’s suffering is never-ending. Not only has he been dragged back to this accursed university that it feels like he _just_ managed to escape, but Cichol quickly abandoned him to go off looking for Seiros.

“Leave her be,” Macuil had reasoned. “She doesn’t want to be found, and do you really want to take the risk of waking her if she’s still angry? Her temper’s a hundred-fold worse than mine!”

Cichol, the idiot, had stuck his holier-than-thou nose in the air. “ _Rhea_ has shown remarkable self-control by choosing to cool off rather than march for war when she was confronted. I’m sure it will be just fine.”

If they kept at it, there would inevitably be a tussle. Even Macuil knew better than to start a real fight in the midst of so many squishy humans, so that had been the end of that.

Shortly after, Cethleann received a call to “hang out” with friends, so here he is looking for Indech on his own. Macuil strides across the campus that he couldn’t forget even if he tried, occasionally glaring down anyone who recognizes him and might like to start up a chat. One of the first places he looks is the pond, for obvious reasons.

The sun has just set, and the first stars of the night twinkle above the remaining streaks of pink and indigo. The humid summer air is filled with insect song. And instead of seeing a man sitting by the reeds, there’s a sacred beast in the center of the small body of water. His shell is gleaming black, definitely freshly scrubbed and polished. There are fairy lights strung around its circumference, and a tent-like blanket structure in the center of his back.

Macuil slowly backs away from the insanity that has obviously overtaken his brother in the centuries he’s been all alone underwater. Alas. It’s too late. A girl’s head pokes out from the strange blanket structure on top of Indech. She spots him and immediately retracts back in as if she were also a turtle made of quilts. However, she must have alerted her host.

“Macuil!” Indech swims over in beast form. “I’ve been expecting you! Come, come join me and my granddaughter for a sleepover!”

**Notes for the Chapter:**

> Turtle Grandpa adopts Bernie and disowns her dad. Then he adopts Hanneman too and treats the distinguished old professor like a young lad even though Turtle Grandpa appears forever in his 30s.


End file.
